Fuel injection valves which operate electromagnetically are well known. With the aid of a magnetic coil which is chargeable by electricity to generate a magnetic field, a magnetisable armature, which may be combined with a valve needle, will be stimulated for movement. Normally, the movement is an axial movement along a valve needle axis of the valve needle.
If the valve needle and the armature are coupled, the valve needle also starts moving due to the movement of the armature. Depending on the direction of the movement, a nozzle orifice may be opened or closed with the aid of the valve needle. In order to seal the nozzle orifice when the magnetic coil is not energized, a first spring element is normally positioned in the fuel injection valve, which urges the valve needle against the nozzle orifice. This means, that the valve needle has to be moved by the aid of the armature against the spring force of the first spring element, when the nozzle orifice is to be opened. When the nozzle orifice is open, a fuel quantity, positioned in the fuel injection valve, can flow through the nozzle orifice into a combustion chamber, normally a combustion chamber of an internal combustion engine.
A combustion process of the internal combustion engine depends—among several other criteria, e.g. fuel quantity or fuel temperature or fuel pressure—on the opening and closing transients of the nozzle orifice. Therefore, an exactly defined opening and closing of the nozzle orifice are very important for reaching an advantageous power rate, fuel consumption and/or emissions of the internal combustion engine.
European patent EP 1 137 877 B1 discloses an exemplary fuel injection valve. The fuel injection valve has an armature which is formed by two pieces. So the armature comprises a first armature part and a second armature part.
One problem of the fuel injection valves in the state of the art is a non-linearity of a fuel injection rate depending on a pulse width of the nozzle orifice. Linearity of the fuel injection rate may be achieved only with greater pulse width.